Innovative materials for emerging photovoltaics

This work explores the development of innovative and sustainable materials for dye-sensitized solar cells (DSSCs), addressing key challenges related to efficiency, transparency, and environmental impact. The research focuses on three main aspects: near-infrared (NIR) dyes, water-based electrolytes, and squaraine dyes, with the aim of advancing semi-transparent photovoltaic technologies for applications such as building-integrated photovoltaics (BIPV). NIR cyanine dyes were investigated to extend light absorption beyond the visible spectrum while maintaining high transparency. The VG20-C16 dye exhibited strong absorption in the NIR region and high color rendering index, enabling the fabrication of nearly colorless and semi-transparent devices. Optimization of dye concentration, dipping time, and temperature showed that standard concentration and room-temperature conditions provide the best photovoltaic performance. Additionally, new cyanine dyes were synthesized and evaluated, with VG20-C16 and VG28 derivatives demonstrating the most promising balance between power conversion efficiency (PCE) and optical transmittance. To improve sustainability, water-based electrolytes were developed as alternatives to conventional organic solvents. These systems offer advantages in safety, cost, and environmental compatibility. The application of TiCl₄ treatment significantly enhanced device performance, increasing short-circuit current density and open-circuit voltage. Electrochemical impedance spectroscopy (EIS) analysis revealed two major limiting factors in aqueous DSSCs: ionic diffusion resistance and interfacial recombination processes. Furthermore, seawater-based electrolytes were explored as an abundant and low-cost resource, achieving comparable photovoltaic performance while maintaining good stability. Finally, squaraine dyes were studied due to their strong NIR absorption and tunable electronic properties. Structural modifications, such as the incorporation of barbituric or benzothiophenone dioxide groups, enabled spectral tuning and improved device performance. Among the investigated systems, certain squaraine dyes exhibited superior results in both organic and aqueous electrolytes, achieving a favorable compromise between PCE, average visible transmittance (AVT), and light utilization efficiency (LUE). Overall, this work demonstrates that the integration of NIR-absorbing dyes with environmentally friendly electrolytes represents a viable strategy for the development of efficient, semi-transparent, and sustainable DSSCs, contributing to the advancement of next-generation photovoltaic technologies.